Counter A Virtual Presence Counter

This paper describes a new measure for presence in immersive virtual environments (VEs) based on data that can be obtained unobtrusively during the course of a VE experience. At different times during an experience a participant will occasionally switch between interpreting the totality of sensory inputs as forming the VE or the real world. The number of transitions from virtual to real is counted, and using some simplifying assumptions, a probabilistic Markov Chain model can be constructed to model these transitions. This can be used to estimate the equilibrium probability of being 'present' in the VE. This technique was applied in the context of an experiment to assess the relationship between presence and body movement in an immersive VE. The movement was that required by subjects to reach out and touch successive pieces on a Tri-Dimensional chess board. The experiment included 20 subjects, 10 of whom had to reach out to touch the chess pieces ('active group'), and the other 10 controls only had to click a hand-held mouse button. The results showed that amongst the active group there was a significant positive association between body movement and presence. The result lends support to interaction paradigms that are based on maximizing the match between sensory data and proprioception.